1. Field of the Invention
Electric pre-weld heaters.
2. Prior Art
A relatively new product which has achieved some substantial success is constituted by an electric pre-weld heater. An elongated U-shaped heater is supplied with current sufficient to cause the heater coil in parallel legs of the unit to heat up the work pieces being welded together. The localized preheating of steel for arc welding is a prime necessity in high-stress areas of metal construction. The prior art electric pre-weld heaters used in localized weld pre-heating ensure compatibility with an arc welding process as well as maintaining high strength and ductility of the weld areas generally equal to the parent metal.
The localized, electric pre-weld heaters are a tubular style using a high temp alloy sheath material with a helical heat coil imbedded in magnesium oxide. The sheath is formed into a hairpin configuration, maybe then flattened on one side to increase the contact surface to the parent metal if desired. The terminal ends are bent up to prevent the plugs and wire from contacting the hot surface. Mounting brackets are provided across the hairpin at various locations. The brackets are placed over tackwelded threaded studs on the metal and are drawn up tight using bolts. The heaters normally are annealed to facilitate bending them to fit slightly curved surfaces. Various shapes of the pre-weld heaters have been provided by the prior construction.